Numerous monitoring systems exist which provide a sensory, status indication of an environment or condition under watch. Alarm systems serve to monitor unwarranted intrusions to areas or equipment; smoke contamination; equipment parameter and operational conditions; and other conditions or circumstances.
Typically there is a primary source of power to operate these systems. It is usually derived from the principal, AC electrical energy otherwise available at a location for the lighting and other power needs of the site.
Of course, the obvious concern with these AC powered systems is how they will perform when there is a power failure, so that the primary source of energy is unavailable. Backup power systems are a necessity.
Many monitoring systems included DC battery, power supplies which are interfaced with the circuitry so as to permit a switch over when there is a failure; and a cutout when primary AC power is restored. Without more, this is sufficient for short term AC power failures, as long as the power drain from the battery, for the period of time involved, does not exceed its amp-hour capacity.
Unfortunately, although the power drain of the system is ascertainable, the period of interruption, in may cases, is not. So, unless there is a way to augment or replenish the DC battery power, this basic system is impractical, except for highly predictable circumstances.
One straight forward solution would be to increase the size and/or number of batteries providing the backup power. Of course the obvious, logistical drawbacks of such an approach due to weight and size discourage its use.
If a suitable approach to replenishing the spent dc power were available, this would address the problem. One such general approach utilizies the “endless” or “free” source of energy, the sun, to recharge the batteries. Numerous, specific adaptations exist including those described in the following U.S. Pat. No. 4,862,141; apparently U.S. Pat. No. 5,883,527 (see below); U.S. Pat. Nos. 5,438,225; 5,563,456; 4,890,093 and 4,764,757.
In U.S. Pat. No. 4,862,141, a bank of solar cells charges a battery that powers both the smoke detector and intrusion alarm. This system uses the solar cells as a primary source of power. House current is not used to supply power to the alarm and detector. This is not a backup system.
In the embodiment of FIG. 2 of U.S. Pat. No. 5,883,577, house current normally supplies power to the smoke detector. In the event of power outage, battery 21, charger/regulator 22, and solar cell array 13 somehow provide power to the detector. No schematic is given, so the nature of this circuit is unclear. In the event the backup battery 21 is removed or damaged, somehow the solar cell array 13 and charger/regulator 22 will supply power to the detector. The second embodiment of FIG. 5 has two chargers/regulators. One charger/regular is powered by house current and normally supplies power to both operate the detector and also trickle charge the battery 21. In the event of a power outage, this same charger/regulator supplies power to the detector, presumably from battery 21 or solar cell array 13 (but at col. 4, lines 9 through 16, the specification seems to be saying that the battery is now somehow charged during power outage). In the event the battery 21 is damaged or removed the other charger/regulator somehow comes into play and draws power from the solar cell array to power the detector.
In U.S. Pat. No. 5,438,225, a solar cell 15 (FIG. 3) operates through regulator 16 as the primary power source for voltage at terminal 40. Cell 15 normally charges backup battery 18 through charger 19. If cell voltage is low, battery 18 then provides power. If voltage sensor 41 detects a low battery voltage, it closes switch 42 to draw power from the capacitive discharge ignition system, to provide power through regulator 45 to terminal 40. See also U.S. Pat. No. 5,563,456, which is a CIP of the ′225 patent.
In U.S. Pat. No. 4,890,093, solar cell 1 charges battery 3 through blocking diode 2. Battery 3 provides power to the converter block 2, which supplies power to the motion sensor in block 4. Motion sensed by block 4 produces a persistent signal that is sent to block 3 to illuminate the security light 10, if: (1) photocell 11 indicates a relatively dark ambient, and (2) the voltage from battery 3 is sufficiently high.
In U.S. Pat. No. 4,764,757, a security system has a number of stations that can activate several alarms when distress signals are received from a portable transmitter. The stations each have a solar cell that trickle charges a battery. The battery is the primary power source for the alarms.
In these various patents solar cells may be utilized as part of the primary source of power and not a part of a backup circuit design. Alternately they form a part of a battery charging system as well as the primary source of power, so that the battery can provide power, if the cell voltage is too low. Trickle current circuitry is described in at least one of the patents as the mechanism for charging the battery.
Although these patents detail various solutions, the approach of the present invention is unique and accomplishes the primary object of providing an intelligent control of the charging of an integral 12 volt DC back up battery from a solar panel array.
Further the present invention realizes the additional advantages by providing:
1) means to monitor the presence of local AC power and to detect and signal the loss of said local AC power;
2) means to include or ignore the local alarm panel's supervisory “flag” as to the status of local AC power presence;
3) means to connect in parallel (“tag on”) the integral solar charged battery to the panel backup battery terminals under the conditions of local AC power loss and to disconnect the integral battery upon return of local AC power;
4) means to sense the backup battery voltage level going below a predetermined DC voltage and to disconnect the backup battery from the “tag on” subsystem and solar charger upon detection of said condition and to signal said condition, and conversely, the means to connect the backup battery to the “tag on” subsystem and solar charger when the voltage level rises above the predetermined threshold; and,
5) means to deliver system status information to outside systems by way of terminal block connections.
Toward the accomplishment of these objects and advantages, a preferred embodiment of the unique backup unit of the present invention is described. A full understanding will be facilitated by reference to the accompanying drawings which are described in the following section. After a reading hereof a further appreciation of the stated objects and advantages as well as others will be apparent.